This invention relates to a rotation control device for a disc player, more particularly a compact disc player for the compact disc system.
In the compact disc which is digitally recorded with audio information, information is recorded at a constant linear velocity and, for securing this constant linear velocity in reproducing this information, a control of disc rotation is performed through a phase control operation on the basis of phase difference data obtained by comparing a frame synchronizing signal produced from a reproduced EFM signal with an internal synchronizing signal produced by an internal clock generator.
In a case where an actual rotation speed of the disc is largely deviated from a normal linear velocity, it is extremely difficult to promptly restore the rotation speed to a stable one only by this phase control operation. Also in a case where a reproduced EFM signal has become unavailable for such a reason that the light beam has become out of focus during reproduction of the recorded information, the phase difference data becomes unavailable with a result that the disc rotation can no longer be controlled at a constant linear velocity.